advanced variation of a circuit that changes flow direction of current given to an electric motor such as a gear motor for instance that moves a solar panel...etc. It follows precisely. It can be used as a locator of any kind of source depending on the input interface. Here in this example it's another Wheatsone Bridge made by normal resistances. You can replace that potentiometer with a PTC, NTC, LDR...etc that can provide a change of the electric potential within the WB. Equal potential means NO reaction (poti in middle position!)...negative turn the motor anti clockwise and positive turns it clockwise. The OP's amplify and steer one or the transistor circuit. One at a time. So it will follow precisely the sun or any other energy source depending on your interface you attach. Instead of a motor I used two LED's for you to see the output reactions. Easy as that and it's very accurate and reliable. Find more useful things to do for this circuit. You can use two of them to cover 3dimensional follow ups...Enjoy! Have fun.
